Theories About Light Part1: Visible Light and Intensity
Intensity: The candela is the basic unit in photometry. All other luminous quantities can principally be derived from it. The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 Hertz and that has a radiant intensity in that direction of 1/683 Watt per Steradian. One steradian [...]
